The present invention relates, according to a first aspect, to one for cooling of electronic- and/or computer equipment in a station. According to a second aspect, the invention relates to an air guiding device which is especially suited to be utilized in such a cooling system. According to a third aspect, finally, the invention relates to one for cooling of such equipment.
Power for operation of the cooling systems which serve medium sized and big telephone exchanges normally costs between 40% and 75% of the power for operation of the exchange itself.
Normally such systems are served by cooling agent compressors, which require big resources with regard to operation, attendance and maintenance. Besides, the cooling agents, which are normally used in such, are harmful to the environment if they should leak out.
Efforts therefore have been made to manage the problems which have been related to conventional technology in the field. Consequently there is described in SE 95-02322-2 a cooling system which is more power saving, more reliable, requiring less maintenance and in addition is more friendly to the environment due to the fact that freon or other harmful fluor containing cooling agents are not used.
A cooling system of this kind is based on the fact that the temperature in the cooling battery is only a few degrees lower than the temperature in the equipment.
At that air at low speed is sucked in through an inlet part of the battery. The air is at that warmed up by the equipment. By depression effected by the circulation fan, sufficient operation power is given to make it pass the cooling battery where it is cooled.
When the air after that has passed the circulation fan and is pressed out through its outlet, it will have a high degree of turbulence, which also means partially high speeds and high dynamic pressures.
According to Bernoulli""s equation there will be low statical pressures in parts of the outgoing air flow.
Ptot=P1+0,5xc2x7xcfx81xc2x7V2,
where
Ptot=total pressure
P1=static pressure,
and
0,5xc2x7xcfx81xc2x7V2=dynamic pressure
The low static pressure, which will be a consequence of the turbulent flow, causes a problem by air from the surroundings tending to be sucked into the cooling air flow. This will result in that, in the first place, there will be a very disadvantageous distribution of speed over the surface which constitutes outlet for the cooling air and where the speed in the part which is closest to the fan will be in wrong direction. In the second place, the outgoing air flow will be a number of degrees warmer than if the cooled down process air could reach the equipment directly. This as a consequence of the air which is mixed into it from the surroundings.
One way to compensate this could be to reduce the temperature in the heat transfer medium to the battery. This, however, would require considerably increased cooling power and in addition not be in accordance with the concept according to the above mentioned Swedish patent application where operation with high heat transfer medium temperatures for free cooling is applied.
The objective of the present invention is, in the light of this, to try to effect the cooling in such a way that the above discussed increase of the temperature of the air, in its path from the battery to the equipment, is avoided.
Owing to that the air guiding devices in the system which guide the air from the battery to the equipment have double chambers, laminar flow can be obtained from the air guiding device if one sees to it that the partition wall which separates these is designed as a low impulse device with such a flow resistance that in the first chamber a static pressure is built up which is exactly adjusted to bridge the static pressure in the second pressure chamber, which gives as close a laminar flow as possible, so that temperature increasing mixing in of warm surrounding air is eliminated, or is at least strongly reduced. To this will also contribute the fact that the design with two chambers separated by the impulse device gives possibility to, by suitably directed angle of the impulse device, effect one on the whole uniform speed of the air flow, which further reduces the risk of mixing in of warmer air.
The invention is especially intended to be utilized, and its advantages will be especially prominent, when the cooling battery is of a kind which communicates with one outside the room located cooler via pipe lines for heat transfer medium, especially of the kind which operates with small temperature differences, by which here is meant totally less than 5xc2x0 C. Such an application of the invention therefore constitutes a preferred embodiment of the invention.
The invention is especially effective when the fan of the system is located on the outlet side of the battery, because the problem with air turbulences then is most accentuated. Such an embodiment therefore constitutes a preferred embodiment of the invention.
Suitably the impulse device consists of an air pervious partition wall, which is a simple and appropriate way to realize this. By that a good result is effected if the partition wall consists of a plate with perforations of suitable allocation and size. The perforated plate is preferably completed with a filter mat/cloth.
In another preferred embodiment of the system the partition wall is slanting so that air flowing into the first chamber has a direction which deviates more from the perpendicular direction towards the plane of the partition wall than the flow direction of the outlet air from the second chamber. This is of great importance to effect the homogenous distribution of speed, at which the angle of the plate is selected with this in view.
The invented system is in one embodiment designed with battery and air guiding device in a separate room, separated from the equipment room, which can be one in some applications advantageous alternative.
At an alternative preferred embodiment of the invention the air guiding device is instead designed as a special air guiding device. This has great advantages because old stations can utilize these and they can be located in the equipment room itself. Further, a production in series, and by that rational production of such air guiding devices, can be made.
According to preferred embodiments of the invented procedure, it is applied at a system according to the first aspect of the invention and/or at utilization of an air guiding device according to the second aspect of the invention.